Regulation of vascular smooth muscle cell plasticity

描述(申请人提供)：VSMC表型的调节仍然是血管平滑肌细胞(VSMC)生物学中尚未回答的关键问题。VSMC保持着显著的可塑性，可以去分化并重新进入细胞周期，从而允许生长和愈合。然而，这种可塑性也可能导致严重的血管病变，包括再狭窄、移植失败、动脉粥样硬化和移植血管病变。值得注意的是，尽管进行了密集的研究，但调控VSMC可塑性的过程在很大程度上是未知的，几乎没有成功针对这一过程的治疗方法。随着越来越多的患者患有血管疾病，迫切需要发现新的靶点。我们已经有了令人兴奋的发现，去分化的VSMC表达与干细胞多能性相关的基因，包括Sox2，Oct4，Nanog和KLF4。我们认为这些干细胞相关基因解释了成熟VSMC独特的可塑性。最近的突破性研究已经确定染色质修饰蛋白的TET(十-十一易位)家族是胚胎和造血干细胞多能性的关键介质。我们的初步结果表明，TET2是VSMC表型的表观主调控因子。重要的是，我们发现TET2抑制干细胞相关基因和去分化表型的经典标记的表达。我们先前发现mTORC1抑制剂雷帕霉素促进VSMC分化。我们现在发现雷帕霉素调节TET2的表达。值得注意的是，我们发现TET2还调节miRNAs，后者可以调节分化特异性和干细胞相关基因的表达。我们假设TET2是VSMC表型的主要调节者，它通过协调调节收缩和干细胞相关基因的启动子，以及miRNAs。在特定的目标1中，我们将确定干细胞相关基因在VSMC表型中的作用。在特定的目标2中，我们将确定TET2调节的miRNAs在VSMC表型中的作用。在特定的目标3中，我们将确定靶向TET2或干细胞相关基因在体内内膜增生模型中是否具有治疗作用。如果我们的目标实现，我们将确定VSMC可塑性的新机制。了解mTORC1调节VSMC表型的关键机制将有助于心血管治疗的改进。

DESCRIPTION (provided by applicant): Regulation of VSMC phenotype remains a key unanswered question in vascular smooth muscle cell (VSMC) biology. VSMC retain a remarkable plasticity to de-differentiate and re-enter the cell cycle allowing for growth and healing. However, such plasticity can also contribute to severe vascular pathologies, including restenosis, graft failure, atherosclerosis, and transplant vasculopathy. Remarkably, despite intense study, the process regulating VSMC plasticity is largely unknown with few therapies successfully targeting this process. With the growing numbers of patients suffering from vascular disease the discovery of novel targets is urgently warranted. We have made the exciting discovery that de-differentiated VSMC express genes associated with stem cell pluripotency, including Sox2, Oct4, Nanog, and KLF4. We propose that these stem cell-associated genes account for the unique plasticity of mature VSMC. Recent groundbreaking studies have identified the TET (ten-eleven translocations) family of chromatin modifying proteins as key mediators of pluripotency in embryonic and hematopoietic stem cells. Our Preliminary Results implicate TET2 as an epigenetic master regulator of VSMC phenotype. Importantly, we find that TET2 inhibits expression of stem cell-associated genes and classic markers of the de-differentiated phenotype. We previously discovered that the mTORC1 inhibitor, rapamycin, promotes VSMC differentiation. We now find that rapamycin regulates TET2 expression. Remarkably, we find that TET2 also regulates miRNAs that can modulate both differentiation-specific and stem cell-associated gene expression. We hypothesize that TET2 is a master regulator of VSMC phenotype through its coordinated regulation of the promoters of contractile and stem cell-associated genes, as well as of miRNAs. In Specific Aim 1, we will determine the role of stem cell-associated genes in VSMC phenotype. In Specific Aim 2, we will determine the role of TET2-regulated miRNAs in VSMC phenotype. In Specific Aim 3, we will determine whether targeting TET2 or stem cell-associated genes has therapeutic utility in in vivo models of intimal hyperplasia. If our goals are achieved, we will have identified a nove mechanism underlying VSMC plasticity. Understanding the critical mechanisms by which mTORC1 regulates VSMC phenotype will lead to improved cardiovascular therapeutics.